Bench and pilot scale testing has shown that biooxidation of a refractory arsenical sulphide concentrate enhanced gold and silver extraction by cyanidation. Direct cyanidation of Southern Tail bulk sulphide concentrate typically resulted in less than 10% gold and silver recovery. Biological pretreatment of the sulphide
concentrate resulted in 70% gold extraction and at least 30% silver extraction within economic process constraints.
Biooxidation of a low grade arsenical sulphide concentrate, 5.5 g Au/t, 80 g Ag/t, and 2-5% As, was economically attractive due to apparent preferential oxidation of the gold bearing suphide mineral assemblage(s). Selective sulphide oxidation minimized the bioleach residence time, the oxygen/CO₂ requirements, and the costs associated with neutralization of the acidic byproducts of sulphide oxidation. Approximately 15% total sulphide
oxidation was required to effect 70% gold extraction and 30-40% silver extraction. Additional sulphide oxidation improved gold extraction slightly and improved silver extraction significantly but was not economically
attractive. Complete batch and continuous laboratory bioleach facilities were constructed at Equity. A detailed
description of apparatus, methods, and operating data is presented. Critical variables that were studied included temperature, pH, pulp density, particle size, air/CO₂ requirements, nutrients, bioleachate recycle, inoculum source, degree of sulphide oxidation, cyanidation conditions, and bioleachate treatment. The laboratory data provided the design and operating criteria for a continuous bioleach pilot plant.
Operation of the continuous pilot circuit, with a nominal design capacity of 2 tonnes per day, showed there was no significant effect of scale on the biohydrometallurgy or resultant precious metals hydrometallurgy. A detailed description of the pilot equipment and steady state operating parameters is presented. Considerations for scaleup and for plant scale design and optimization are discussed.
A preliminary feasibility study, based on a conceptual design for an 800 tonne per day bioleach circuit, is detailed. The feasibility analysis showed that it is economically attractive to scavenge gold and silver values from Southern Tail flotation tailing using biooxidation to enhance the gold and silver extraction by cyanidation. The base case cash flow analysis showed a Net Present Value potential of $4,975 x 106 (1985) at 15% discount factor. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/26314 |
| Date | January 1986 |
| Creators | Marchant, P. Brad |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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